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Asymmetric synthesis of quinoline-naphthalene atropisomers with fully blocked ortho positions has been developed by a two-step strategy, which contains a chiral phosphoric acid-catalyzed Povarov reaction and a DDQ oxidation reaction. This method provides facile access to diverse functionalized quinoline-naphthalene atropisomers with one or two chiral axes in excellent yields (≤98%) and excellent enantioselectivities (≤99% ee).

Endothelial nitric oxide synthase (eNOS) encoded by nitric oxide synthase 3 (NOS3), can generate nitric oxide (NO) which serves as an important deterrent to the pathogenesis of thrombosis by modulating the activation, adhesion and aggregate formation of platelets. Three serum miRNAs (miR-195, miR-532 and miR-582) have been suggested as biomarkers for the diagnosis of deep vein thrombosis (DVT), however their potential roles in DVT is not clear. The effect of miRNAs inhibiting the expression of NOS3 was evaluated in vitro. miR-195, miR-532 and miR-582 mimic, inhibitor, and control miRNAs were transfected into endothelial cells. The roles of miR-195, miR-532 and miR-582 regulating the expression of eNOS were evaluated by real-time quantitative PCR, Western Blotting and luciferase reporter assays. NO release was measured by Griess method. We confirmed NOS3 as a direct target of miR-195 and miR-582, which binds to the 3'-UTR of NOS3 mRNA in endothelial cells. A significantly inverse correlation between these two miRNAs and eNOS expression was detected. NO release from endothelial cells was decreased when the expression level of miR-195 and miR-582 was up-regulated. These findings indicated that miR-195 and miR-582 regulated NO release by targeting 3'-UTR of NOS3 post-transcriptionally in endothelial cells. Therefore, miR-195 and miR-582 might play an important role in maintaining endothelial NO bioavailability and could be a novel target for treatment of thrombotic diseases.

Background CRISPR-Cas9 has been developed as a therapeutic agent for various infectious and genetic diseases. In many clinically relevant applications, constitutively active CRISPR-Cas9 is delivered into human cells without a temporal control system. Excessive and prolonged expression of CRISPR-Cas9 can lead to elevated off-target cleavage. The need for modulating CRISPR-Cas9 activity over time and dose has created the demand of developing CRISPR-Cas off switches. Protein and small molecule-based CRISPR-Cas inhibitors have been reported in previous studies. Results We report the discovery of Cas9-inhibiting peptides from inoviridae bacteriophages. These peptides, derived from the periplasmic domain of phage major coat protein G8P (G8PPD), can inhibit the in vitro activity of Streptococcus pyogenes Cas9 (SpCas9) proteins in an allosteric manner. Importantly, the inhibitory activity of G8PPD on SpCas9 is dependent on the order of guide RNA addition. Ectopic expression of full-length G8P (G8PFL) or G8PPD in human cells can inactivate the genome-editing activity of SpyCas9 with minimum alterations of the mutation patterns. Furthermore, unlike the anti-CRISPR protein AcrII4A that completely abolishes the cellular activity of CRISPR-Cas9, G8P co-transfection can reduce the off-target activity of co-transfected SpCas9 while retaining its on-target activity. Conclusion G8Ps discovered in the current study represent the first anti-CRISPR peptides that can allosterically inactivate CRISPR-Cas9. This finding may provide insights into developing next-generation CRISPR-Cas inhibitors for precision genome engineering.

To provide a vehicle for sustained release of cartilage-protective agent for the potential application of osteoarthritis (OA) treatment, we developed a kartogenin (KGN)-incorporated thermogel for intra-articular injection. We fabricated a poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PLGA–PEG–PLGA) thermogel as a KGN carrier for IA injection. OA chondrocytes were cultured in thermogel with or with no KGN to investigate the effect of KGN thermogel on cartilage matrix. The in vivo effect of KGN thermogel on OA was examined in a rabbit OA model. The KGN thermogel showed a sustained in vitro release of KGN for 3 weeks. OA chondrocytes proliferated well both in thermogel and KGN thermogel. In addition, OA chondrocytes produced higher amount of [type 2 collagen (COL-2) and glycosaminoglycan (GAG)], as well as lower level of matrix metalloproteinase 13 (MMP-13) in KGN thermogel that those in thermogel with no addition of KGN. The gene analysis supported that KGN thermogel enhanced expression of hyaline-cartilage specific genes Col 2 and AGC, and inhibited the expression of MMP-13. Compared with intra-articular injection of saline or thermogel containing no KGN, KGN thermogel can enhance cartilage regeneration and inhibit joint inflammation of arthritic knees in a rabbit ACLT-induced OA model at 3 weeks after the injection. Therefore, the KGN-incorporated PLGA–PEG–PLGA thermogel may provide a novel treatment modality for OA treatment with IA injection.

A vertical flow constructed wetland was combined with a biological aerated filter to develop an ecological filter, and to obtain the optimal operating parameters: The hydraulic loading was 1.55 m 3 /(m 2 ·d), carbon–nitrogen ratio was 10, and gas–water ratio was 6. The experimental results demonstrated considerable removal efficiency of chemical oxygen demand (COD), ammonia nitrogen (NH 4 + -N), total nitrogen (TN), and total phosphorus (TP) in wastewater by the ecological filter, with average removal rates of 83.79%, 93.10%, 52.90%, and 79.07%, respectively. Concentration of NH 4 + -N after treatment met the level-A discharge standard of GB18918-2002. Compared with non-plant filter, the ecological filter improved average removal efficiency of COD, NH 4 + -N, TN, and TP by 13.03%, 25.30%, 14.80%, and 2.32%, respectively: thus, plants significantly contribute to the removal of organic pollutants and nitrogen. Through microporous aeration and O 2 secretion of plants, the ecological filter formed an aerobic–anaerobic–aerobic alternating environment; thus aerobic and anaerobic microbes were active and effectively removed organic pollutants. Meanwhile, nitrogen and phosphorus were directly assimilated by plants and as nutrients of microorganisms. Meanwhile, pollutants were removed through nitrification, denitrification, filtration, adsorption, and interception by the filler. High removal rates of pollutants on the ecological filter proved that it is an effective wastewater-treatment technology for decentralized wastewater of mountainous towns.

Direct polymerization of allyl alcohol generally results in low molar mass oligomers or highly branched or cross-linked structures, and the properties and applications of linear, high molar mass poly(allyl alcohol) (PAA) are relatively unexplored. Such macromolecular materials that cannot otherwise be obtained directly can be accessed by postpolymerization modification strategies. Herein we describe the synthesis and characterization of linear, high molar mass PAA by borohydride reduction of a new activated polyacrylamide. The facile polymerization and mild reduction conditions enable the preparation of PAA of targeted molar masses and low dispersity, as well as PAA block polymers via chemoselective reduction of the activated amide moiety.

Therapeutic proteins have shown great potential in treating life-threatening diseases, but the hydrophilicity and high molecular weight hamper their passing through the cell membrane. Cell-penetrating peptide (CPP)-assisted protein delivery is a simple and efficacious strategy to promote the cellular uptake of therapeutic proteins. We recently demonstrated that the engineered Cys2-His2 zinc-finger domains possess intrinsic cell permeability, which could be leveraged for intracellular protein delivery. Here we applied this method to deliver superoxide dismutase (SOD), a therapeutic protein widely used in preclinical and clinical studies. We present a protocol for the production and delivery of zinc-finger domain-fused SOD. This protocol can be extended for delivering other therapeutic proteins.

Synthetic polymeric scaffolds are commonly used in bone tissue engineering (BTE) due to their biocompatibility and adequate mechanical properties. However, their hydrophobicity and the lack of specific cell recognition sites confined their practical application. In this study, to improve the cell seeding efficiency and osteoinductivity, an injectable thermo-sensitive chitosan hydrogel (CSG) was incorporated into a 3D-printed poly(ε-caprolactone) (PCL) scaffold to form a hybrid scaffold. To demonstrate the feasibility of this hybrid system for BTE application, rabbit bone marrow mesenchymal stem cells (BMMSCs) and bone morphogenetic protein-2 (BMP-2) were encapsulated in CSG. Pure PCL scaffolds were used as controls. Cell proliferation and viability were investigated. Osteogenic gene expressions of BMMSCs in various scaffolds were determined with reverse transcription polymerase chain reaction (RT-PCR). Growth factor releasing profile and mechanical tests were performed. CCK-8 assay confirmed greater cell retention and proliferation in chitosan and hybrid groups. Confocal microscopy showed even distribution of cells in the hybrid system. After 2-week osteogenic culture in vitro, BMMSCs in hybrid and chitosan scaffolds showed stronger osteogenesis and bone-matrix formation. To conclude, chitosan/PCL hybrid scaffolds are a favorable platform for BTE due to its capacity to carry cells and drugs, and excellent mechanical strength.

Sarsasapogenin, extracted from Anemarrhena asphodeloides Bunge., has been reported to protect neurons from H 2 O 2 -induced damage. In the current study, four series of 26-amino acid methyl ester substituted sarsasapogenin derivatives ( 5a – 5e , 5f – 5j , 6a – 6e and 7a – 7e ) were synthesized and tested for neuroprotective activity by evaluating their neuroprotective ratio against SH-SHY5Y cell lines. Studies showed that most of the target compounds displayed better neuroprotective effects than that of sarsasapogenin. Structure-activity relationship analysis suggested that 3-methoxy derivatives ( 5f – 5j ) were more potent than other series and the phenylalanine methyl ester moiety at C-26 was important for exhibiting apparent neuroprotective activity. It was worth noting that compound 5h exhibited optimal neuroprotective activity (102.2%) compared with sarsasapogenin (27.3%) and trolox (40.5%), and this encouraged us to investigate the cellular mechanism of 5h further. Our investigation revealed that 5h could attenuate H 2 O 2 -induced cell damage by inhibiting the expression of cleaved poly (ADP-ribose) polymerase (PARP) and cleaved caspase-3 as well as rescuing the downregulation of brain-derived neurotrophic factor (BDNF) and its tyrosine receptor kinase B (TrkB). Taken together, these results suggest that the representative compound 5h is a profound lead compound for further investigation and the sarsasapogenin skeleton could be a promising structural template for the development of new anti-Alzheimer drug candidates.

Background: Total meniscectomy leads to knee osteoarthritis in the long term. The poly(ε-caprolactone) (PCL) scaffold is a promising material for meniscal tissue regeneration, but cell-free scaffolds result in relatively poor tissue regeneration and lead to joint degeneration. Hypothesis: A novel, 3-dimensional (3D)–printed PCL scaffold augmented with mesenchymal stem cells (MSCs) would offer benefits in meniscal regeneration and cartilage protection. Study Design: Controlled laboratory study. Methods: PCL meniscal scaffolds were 3D printed and seeded with bone marrow–derived MSCs. Seventy-two New Zealand White rabbits were included and were divided into 4 groups: cell-seeded scaffold, cell-free scaffold, sham operation, and total meniscectomy alone. The regeneration of the implanted tissue and the degeneration of articular cartilage were assessed by gross and microscopic (histological and scanning electron microscope) analysis at 12 and 24 weeks postoperatively. The mechanical properties of implants were also evaluated (tensile and compressive testing). Results: Compared with the cell-free group, the cell-seeded scaffold showed notably better gross appearance, with a shiny white color and a smooth surface. Fibrochondrocytes with extracellular collagen type I, II, and III and proteoglycans were found in both seeded and cell-free scaffold implants at 12 and 24 weeks, while the results were significantly better for the cell-seeded group at week 24. Furthermore, the cell-seeded group presented notably lower cartilage degeneration in both femur and tibia compared with the cell-free or meniscectomy group. Both the tensile and compressive properties of the implants in the cell-seeded group were significantly increased compared with those of the cell-free group. Conclusion: Seeding MSCs in the PCL scaffold increased its fibrocartilaginous tissue regeneration and mechanical strength, providing a functional replacement to protect articular cartilage from damage after total meniscectomy. Clinical Relevance: The study suggests the potential of the novel 3D PCL scaffold augmented with MSCs as an alternative meniscal substitution, although this approach requires further improvement before being used in clinical practice.

A series of novel hybrid compounds between tricyclic indeno[5,6-b] furan and imidazole has been prepared and evaluated in vitro against a panel of human tumor cell lines. The results suggest that the existence of benzimidazole ring and substitution of the imidazolyl-3-position with a naphthylacyl group were vital for modulating cytotoxic activity. In particular, hybrid compound 26 was found to be the most potent compound against 5 strains human tumor cell lines and more active than cisplatin (DDP), while compound 18 was more selective towards breast carcinoma (MCF-7) and colon carcinoma (SW480) with IC50 value 3.4-fold and 4.3-fold more sensitive to DDP.

As a cell source with large quantity and easy access, peripheral blood mesenchymal stem cells (PBMSCs) were isolated and seeded in porcine demineralized cancellous bone (DCB) scaffolds, cultured in chondrogenic medium and evaluated for in vitro chondrogenesis. Bone marrow MSCs (BMMSCs) and articular cartilage chondrocytes (ACCs) underwent the same process as controls. The morphology, viability and proliferation of PBMSCs in DCB scaffolds were similar to those of BMMSCs and ACCs. PBMSCs and BMMSCs showed similar chondrogenesis potential with consistent production of COL 2 and SOX 9 protein and increased COL 2 and AGC mRNA expressions at week 3 but the COL 2 protein production was still less than that of ACCs. Minimal increase of hypertrophic markers was found in all groups. Relatively higher ALP and lower COL 10 mRNA expressions were found in both MSCs groups at week 3 than that in ACCs, whereas no significant difference of COL 1 and SOX 9 mRNA and MMP 13 protein was found among all groups. To conclude, PBMSCs shared similar proliferation and chondrogenic potential with BMMSCs in DCB scaffolds and could be an alternative to BMMSCs for cartilage tissue engineering. Further optimization of chondrogenesis system is needed regardless of the promising results.

Phase behavior of a supramolecular system based on poly(4-vinylpyridine) (P4VP) and 3,4,5-tris(dodecyloxy)benzoic acid (TDBA) [P4VP(TDBA)x, where x is the molar ratio of TDBA to P4VP repeating unit] was investigated by means of FTIR, differential scanning calorimetry, polarized optical microscopy, and X-ray scattering method. The intermolecular hydrogen-bonding interaction between P4VP and TDBA is confirmed by FTIR. While almost all of the added TDBA molecules are hydrogen bonded to the P4VP chains at x 0.60 and saturates at x > 0.90. The phase structure of P4VP(TDBA)x is composition dependent. At x ∼0.60, the lattice parameter of the cylinder or hexagonal columnar (ΦH) phase decreases with increasing x. Considering the microphas...

The inclusion complexation behavior, characterization and binding ability of alpinetin with hydroxypropyl-β-cyclodextrin (HPβCD) has been investigated in both solution and the solid state by means of UV–vis spectroscopy, FT-IR, 1 H and 2D NMR, XRD, SEM and DSC. The results showed that the water solubility and stability of alpinetin were obviously increased in the inclusion complex with HPβCD. This satisfactory water solubility and high stability of the alpinetin/HPβCD complex will be potentially useful for its application as herbal medicine or healthcare products.

Glutathione S-transferase P1-1 (GSTP1-1, EC 2.5.1.18) is generally conceived to be an important player in the acquired resistance of tumor to anticancer agents, thus a series of quinolinoneacetic acid derivatives were synthesized and their inhibitory effects on GSTP-1 were tested in this study. Interestingly, it was found that some compounds showed remarkable inhibitory effect on GSTP-1 activity. Furthermore, molecular docking study was conducted to provide the binding modes of quinolinoneacetic acid derivatives on GSTP1-1 activity. In summary, we present the discovery of a series of quinolinoneacetic acid compounds as inhibitors of GSTP1-1 and their interaction modes toward GSTP1-1 binding site.

Combining the concept of “flexible spacer” which can bring liquid crystalline (LC) properties to the side-chains and the side-group “jacketing” effect which can result in main-chain with rod-like conformation, we have synthesized a new combined main-chain/side-chain LC polymer based on radical polymerization, poly(2,5-bis{[6-(4-methoxy-4′-oxy-azobenzene)hexyl]oxycarbonyl}styrene) (denoted as P1) with two azobenzene groups per repeating unit. The chemical structures of P1 and the corresponding monomer were characterized using various techniques with satisfactory analysis data. The phase structures and transitions of P1 were investigated using differential scanning calorimetry, polarized optical microscope, and one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction. We identify that P1 can form a hierarchically ordered structure with double orderings on both the nanometer and subnanometer length scales. Most likely, the thick main-chains of P1 obtained by “jacketing” the central rigid portion of ...

Resistance to chemotherapeutic drugs has long been a considerable barrier to successful treatment of many cancers and over-expression of glutathione S-transferase P1-1 is correlated to carcinogenesis and resistance of cancer cells against chemotherapeutic agents. This study throws light on the role of chalcone derivatives, a new class of glutathione S-transferase P1-1 inhibitors potentially to overcome glutathione S-transferase P1-1-mediated chemotherapy resistance. Nineteen alpha-substituted chalcone derivatives were synthesized and their in vitro inhibitory effects on glutathione S-transferase P1-1 were determined. We interestingly found that most of these compounds showed inhibitory effect on glutathione S-transferase P1-1 activity. In addition, molecular field-based similarity analysis provides the necessary three-dimensional molecular field properties of alpha, beta-unsaturated carbonyl derivatives to inhibit glutathione S-transferase P1-1 activity. Thus, these compounds have great potential to be developed into novel chemotherapeutic sensitizers.

During the course of studies directed towards the discovery of novel aldose reductase inhibitors for the treatment of diabetic complications, we synthesized a series of new (Z)-3-phenyl-2-benzoylpropenoic acid derivatives and tested their in vitro inhibitory activities on rat lens aldose reductase. Of these compounds, (Z)-3-(3,4-dihydroxyphenyl)-2-(4-methylbenzoyl)propenoicacid (3k) was identified as the most potent inhibitor, with an IC50 of 0.49 microM. The theoretical binding mode of 3k was obtained by simulation of its docking into the active site of the human aldose reductase crystal structure.

A new type positron beam system is being constructed in Wuhan university. The goal of this project is to build a positron beam which can measure positron lifetimes and has high moderation efficiency. The system utilizes a magnetically guided incident positron beam and the sample is biased to a high negative potential to achieve the desired implantation energies. A conventional tungsten moderator is replaced by a solid Ne moderator with high moderation efficiency (about 1%). A multi-functional target chamber for slow beam studies is designed, which can be used for positron annihilation lifetime spectroscopy (PALS), Doppler broadening (DB) and coincidence Doppler broadening (CDB) measurements.

The epoxy/rectorite nanocomposites with different epoxide equivalent ranging from 188 to 1110 were prepared and the effects of epoxide equivalent on microstructure of materials were studied by X-ray diffraction (XRD) and positron annihilation lifetime spectroscope (PALS). In nanocomposites, the formation of exfoliated structure was observed from XRD pattern at epoxide equivalent >263. The PALS measurements reveal that the fractional free volume in nanocomposites was strongly affected by epoxide equivalent, in particular, the free-volume concentration was dramatically decreased with the increasing epoxide equivalent from 188 to 263, and the S parameter indicates the rectorite structure change and the high sensitivity of positron annihilation to the entry of rectorite into epoxy. These results indicate that positron annihilation characteristics are useful for study the microstructure of epoxy/rectorite nanocomposites.

Undoped Ga-Sb samples were investigated by positron lifetime spectroscopy (PAS) and the coincident Doppler broadening (CDB) technique. PAS measurement indicated that there were monovacancy-type defects in undoped Ga-Sb samples, which were identified to be predominantly Ca vacancy (V-Ga) related defects by combining the CDB measurements. After annealing of these samples at 520 C, positron shallow trapping have been observed and should be due to Ga-Sb defects. Undoped Ga-Sb is intrinsically p-type having a residual carrier density of 10(16)-10(17) cm(-3). And the Ga-Sb antisite defects are stable in the (0), (1-) and (2-) charge states and act as a double acceptor. Thus, we infer that Ga-Sb antisite defects are the acceptor contributing to the p-type conduction for undoped samples. (C) 2004 Elsevier B.V All rights reserved.

A supramolecular side-chain liquid crystalline (LC) polymer P4VP(1)x was prepared using poly(4-vinylpyridine) and a tolane based hemi-phasmid benzoic acid. P4VP(1)x exhibits good processability, forming smectic and hexagonal columnar LC phases at different compositions. Its photoluminescence properties depend on the LC structures.

Based on the fact that timosaponin A-III (TA-III) exhibits potent cytotoxic effects and has been considered as a potential anti-tumor agent, a range of novel sarsasapogenin derivatives 1, 2a-2g, 3, 4, 5, 6a-6g have been synthesized by a simple and facile synthetic route. The in vitro cytotoxic activity of these synthetic compounds has been evaluated against ten human cancer cell lines. The pharmacological results showed that most of the sarsasapogenin derivatives displayed excellent selective cytotoxicity toward the cancer cell lines. An amino group at C-3 or C-26 position of the sapogenin had a profound influence on the cytotoxic activity. In particular, compound 6c exhibited significantly inhibitory activity against A375-S2 (IC50=0.56μM) and HT1080 (IC50=0.72μM) cells. However, introducing a bromo or morpholinyl substituent at the C-3 and C-26 position of the sapogenin generally rendered it inactive against the human cancer cell lines. This research provides a theoretical reference for the exploration of new anti-tumor drugs.

A series of new substituted 3-[4-(phenylsulfonamido)benzoyl]-2H-1-benzopyran-2-one derivatives bearing groups methoxy,tert-butyl, and atoms of halogens at thepara-position of the A-ring were synthesized andin vitrobiological activities were evaluated as nonsugarα-glucosidase inhibitors. Most of the test compounds demonstrated significantα-glucosidase inhibitory activity relative to that of Acarbose (IC50= 29.26 μM). Thepara-substitution with a methoxy group or halogens could notably increase the potency. Compounds17,18, and23, with IC50values of 0.025 μM, 0.014 μM, and 0.018 μM, respectively, may be of significance for the further development of new nonsugarα-glucosidase inhibitors.

Zeolite Y has been used as the host to generate CdS nanoclusters. The location of CdS nanoclusters inside zeolite hosts was confirmed by the blue-shifted reflection absorption spectra with respect to that of bulk CdS materials. But which kind of cage inside zeolite Y, sodalite cage or supercage, was preferred for the CdS clusters remained unclear. In this paper, we conducted positron annihilation spectroscopy (PAS) measurements for the first time on a series of CdS/Y zeolite samples and concluded that CdS clusters were not located in supercages but in smaller sodalite cages. The stability of CdS clusters inside the sodalite units was due to the coordination of Cd atoms with the framework oxygen atoms of the double six-ring windows. Moreover, PAS revealed some important information of surface states existing on the interfacial layers between CdS clusters and zeolite Y.

After Nb 2 O 5 was added to Y 2 O 3 -stabilized ZrO 2 , the bulk conductivity decreased distinctly. Positron annihilation lifetime and Doppler broadening spectra were measured to study the effects of Nb 2 O 5 on electrical properties of Y 2 O 3 -stabilized ZrO 2 . The result shows that the additions of Nb 2 O 5 can decrease the V 2+ O concentration and increase the ( Y − Zr V 2+ O Y − Zr ) 0 concentration, which is why bulk conductivity decreases. The additions of Nb 2 O 5 were expected to suppress the formation of defect associates, however, only adverse experimental results were found in the present work.

Positron lifetime measurements were performed for segmented copolymer poly(ethylene oxide)–poly(ethylene terephthalate) (PEO/PET) as a function of the hard segment content (PET) and the temperature, which is used to study the free volume properties, structural transition and miscibility behaviour of segmented copolymer PEO/PET. From the variation of the ortho -positronium ( o -Ps) lifetimes with changes in the hard segment content, we find that the free volume decreases with increase of the hard segment, this fact means that the hard segment microdomains act as physical cross-links that suppress movement of the chains and that the interactions between the hard segment (PET) and soft segment (PEO) also plays an important role. On the other hand, the temperature dependence of positron lifetimes reveals the existence of two glass transition temperatures. This experimental results show that the hard segment PET is immiscibility with soft segment PEO in segmented copolymer PEO/PET (PEO molecular weight 4000, PET content 30 wt.%). The maximum entropy lifetime method (MELT) is used to detect the distributions of the free volume holes. Large differences in width of the free volume hole distributions as a function of temperature are observed.

Recently polymer nanocomposites[1,2] have been receiving special attention because of its advantages and unique properties in comparison to the traditional polymer composites.The structural transformation of Epoxy (cured by polyamide) and epoxy/Rectorite nanocomposite(with 0.5% rectorite content) is studied by PALS as a function of temperature from 30K to 490K. For Epoxy and Epoxy/Rectorite nanocomposite, the glass transition temperature (Tg) is observed to be 270K and 260K, the second transition temperature (Tγ) is 160K and 120K, the viscous flow temperature (Tf) is the same as 380K. The result shows that properties of the free-volume in nanocomposite have been changed by the rectorite platelets fully separated in material at low temperature. At the same time, we find that the intensity of o-Ps decreases with increase of the temperature at the softening temperature above the Te.

The free volume property and intermolecular interaction (especially hydrogen bonding) of poly (ether-urethane) (PEU) irradiated by neutron under different atmosphere has been studied by positron annihilation lifetime spectroscopy (PALS) and Fourier transform infrared (FTIR). The results suggested that the hydrogen-bonding interactions and free volume property in PEU depended strongly on the neutron irradiation dose.

Hydrogen- and corrosion -related defects of pure iron and AISI 304 and 316 stainless steels were investigated by measuring Doppler broadening energy spectra of positron annihilation. The significant increase in S-parameter after corrosion in iron was interpreted as due to the formation of defects and voids during corrosion processes. However, a decrease of the S-parameter in AISI 304 and 316 stainless steels after corrosion was interpreted as dissolution of passivity oxide film. Furthermore, similar results in iron and stainless steels after hydrogen-charging were observed. Hydrogen damage between the surface and the bulk has a significant variation with depth. The larger increase in S-parameter near the surface after hydrogen-charging mainly comes from the formation of large-size defects (e.g. voids); however the increase in S-parameter in the bulk after hydrogen-charging mainly comes from the production of small-size defects.

The anneal effect of PP/PA/MMT blends had been studied by positron annihilation lifetime spectra (PALS). The o-Ps lifetime and intensity of unannealed blends were linearly additive basis on the PA weight fraction, which was coincident to the simple compound rule. However, the o-Ps intensity of the samples decreased after samples annealed.

MA-g-HDPE and PA6-MMT were selected to improve the compatibility of HDPE and PA6. Positron annihilation lifetime spectroscopy (PALS) and optical microscopy were utilized to characterize the interface of the blends.

Positron spectroscopy was used to study the free volume properties of glassy poly(ethylene terephthalate) as a function of temperature and aging time. The experimental results indicate that the glass transition temperature increases with increasing aging time. This is confirmed by differential scanning calorimetry measurements. From the aging time dependence of the intensity of the ortho-positronium (o-Ps) component I3 and the fractional free volume, we observe that the concentration of free volume holes and the fractional free volume show a continuous decrease at a fixed aging temperature, which suggests that structural relaxation and segmental rearrangement occur during physical aging.

A three-dimensional (3D) composite scaffold was prepared for enhanced cartilage tissue engineering, which was composed of a poly(ε-caprolactone) (PCL) backbone network and a poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PLGA–PEG–PLGA) thermogel surface. The composite scaffold not only possessed adequate mechanical strength similar to native osteochondral tissue as a benefit of the PCL backbone, but also maintained cell-friendly microenvironment of the hydrogel. The PCL network with homogeneously-controlled pore size and total pore interconnectivity was fabricated by fused deposition modeling (FDM), and was impregnated into the PLGA–PEG–PLGA solution at low temperature (e.g., 4 °C). The PCL/Gel composite scaffold was obtained after gelation induced by incubation at body temperature (i.e., 37 °C). The composite scaffold showed a greater number of cell retention and proliferation in comparison to the PCL platform. In addition, the composite scaffold promoted the encapsulated mesenchymal stromal cells (MSCs) to differentiate chondrogenically with a greater amount of cartilage-specific matrix production compared to the PCL scaffold or thermogel. Therefore, the 3D PCL/Gel composite scaffold may exhibit great potential for in vivo cartilage regeneration.

Positron-lifetime measurements have been made for poly (ether urethane) undoped and doped with [LiClO4]/[Unit]=0.05 in the temperature range of 120–340 K. The measured lifetime spectra were resolved into three components. The lifetime and the intensity of orthopositronium were used to evaluate the amount of the free volume in poly (ether urethane). It was found that the variation of ionic conductivity with temperature and salt concentration can be rationalised in terms of free volume consideration.

We have measured the positron lifetime spectra as a function of temperature from 80 to 300 K and Doppler-broadening annihilation radiation (DBAR) spectra in normal and superconducting states for three kinds of Bi-based superconductors: Bi2212, Pb- and F-doped Bi2223. For Pb-doped Bi2223 superconductor, anomalies in the temperature dependence of positron lifetimes indicate the structural instabilities. However, a continuous increasing in the mean lifetime is observed for F-doped Bi2223 system and interpreted in terms of a simple thermal expansion with an average linear expansion coefficient alpha is similar to 35*10(-6). The difference spectra of DBAR spectra after deconvolution between two states show an evidence for charge transfer between the Cu-O and Bi-O planes in Bi-based superconductors. The role of oxygen defects in charge transfer was discussed.

The positron annihilation lifetime spectra of YBa 2 Cu 3 O y superconductors doped with SnO 2 were measured. The results indicate that the tin element substitutes for Cu(1) sites. A brief discussion is given based on the experimental results.

The positron lifetime spectra in polyaniline have been measured as a function of protonation level (pH from 7 to -0.8). We observed that (1) the short lifetime τ 1 decreased with the protonation level; (2) the intermediate lifetime was constant (τ 2 ∼360ps), whereas its intensity I 2 increased with increasing protonation level which was related to the conductivity of material. These results are discussed in terms of conducting island model

The positron lifetime measurements have been performed as a function of temperature for liquid methane and propane and as a function of magnetic field for liquid argon. The long o-Ps lifetime, high o-Ps intensity, and a strong temperature dependence of these values are observed, and interpreted as being due to the Ps localization in the bubble state. The bubble size and surface tension are evaluated using bubble model and o-Ps lifetime. The chemical reaction of Ps atom with oxygen impurities was studied. The reaction rate Kps and its temperature behavior in liquid methane and propane were obtained. The results of magnetic field experiments in both pure and oxygen-added liquid argon show that the lifetime of o-Ps with magnetic quantum number m=0 state decreases basically according to the normal Zeeman effect.

Positron lifetimes in polytetrafluroethylene (PTFE) and polyethylene (PE) have been measured as a function of residual deformation [MATH]. For PTFE, the variation of o-Ps intensity shows a three-stage processes : the elastic region ([MATH]), plastic-f low region ([MATH]) and strain-strengthening region ([MATH]). The changes of free-volume hole size and concentration suggest the separation, scission and orientation of segments. For PE, the o-Ps parameters are sensitive to the elastic and plastic regions. Particularly, the hole concentration decreases linearly with [MATH], which indicates the crystallization during deformation.